Towards understanding the variant effect on the rate of cleavage by chymosin on kappa-caseins A and C
1997
Smith, M.H. | Hill, J.P. | Creamer, L.K. (New Zealand Dairy Research Inst., Palmerston North (New Zealand). Food Science Section) | Plowman, J.E.
The rate of chymosin hydrolysis of kappa-casein C, and consequent micelle coagulation, is slower than that for either kappa-casein A or kappa-casein B. The C variant protein has a histidine residue in position 97 whereas the A and B variants have arginine. The possibility that this change could affect cleavage of the Phe105-Met106 peptide bond has been examined by exploring the relative association of this region of kappa-casein to chymosin using molecular dynamics. From the results it seemed likely that kappa-casein C was bound less tightly to chymosin than either the A or B variant proteins, provided that the His98-Pro99 peptide bond is in the trans configuration, which suggests that the lower concentration of enzyme-substrate complex is responsible for the lower cleavage rate.
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